How to find your (and your cars) limit?
08-25-2017, 10:25 AM
#106
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In A Paddock, just beyond pit lane paddock exit, towards Big Bend and in the middle, with a bunch of other cool cars under the tractor-trailer tent.
Brabham BT-23C, Brabham BT-6, Lotus 23, Lancia Fulvia Zagato, Siata 300BC (bright yellow, baby '50's Ferrari looking, can't miss it) and my cheap car!
See you soon!
Brabham BT-23C, Brabham BT-6, Lotus 23, Lancia Fulvia Zagato, Siata 300BC (bright yellow, baby '50's Ferrari looking, can't miss it) and my cheap car!
See you soon!
__________________
-Peter Krause
www.peterkrause.net
www.gofasternow.com
"Combining the Art and Science of Driving Fast!"
Specializing in Professional, Private Driver Performance Evaluation and Optimization
Consultation Available Remotely and at VIRginia International Raceway
-Peter Krause
www.peterkrause.net
www.gofasternow.com
"Combining the Art and Science of Driving Fast!"
Specializing in Professional, Private Driver Performance Evaluation and Optimization
Consultation Available Remotely and at VIRginia International Raceway
08-25-2017, 11:04 AM
#107
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Though it has limitations due to being based on a particular 2D model, this simulation to determine the optimal line gives an indication of how that can vary with the vehicle: https://www.raceoptimal.com/VIR.
At VIR, the differences are most noticeable from T1 to T3, and from T15 to the front straight. From T3 to T15, the optimal lines are so similar that we could say they're essentially the same. (Again, these conclusions are based on a model which has limitations).
Of course, F1 teams, companies like Porsche, etc. have much more sophisticated simulators, but not easy to get our hands on them!
08-25-2017, 11:17 AM
#108
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Since (a) use of the available grip comes from braking, cornering, and/or acceleration, and (b) pretty much all cars can brake hard enough to use all of the available grip, the biggest variable, by far, in determining the optimal line will be the ratio of power to grip. If that ratio is similar, the optimal line will also be very similar, regardless of engine placement, absolute level of power or grip, etc.
Of course, F1 teams, companies like Porsche, etc. have much more sophisticated simulators, but not easy to get our hands on them!
Of course, F1 teams, companies like Porsche, etc. have much more sophisticated simulators, but not easy to get our hands on them!
On the latter, my opinion is that the limitations of the raceoptimal sim inject serious flaws in the way it calculates the result. I have little actual race and track day data, by leading and proven drivers in a variety of cars, that is close to that generated by raceoptimal. Neat exercise, but of little value, IMO.
Here's an interesting page: http://geneura.ugr.es/cig2012/papers/paper76.pdf
There is Bosch LapSim, but IMO, the easiest, most approachable lap sim software for club level drivers (but suitable for pro teams) is Claude Rouelle's OptimumG sim, OptimumLap.
Take a look here: http://www.optimumg.com/race-prep-an...tion-exercise/
Here is an awesome little article: http://blog.caranddriver.com/the-phy...est-lap-times/
I do have to say, drivers are MOST effective when, as Ross Bentley says, when probing the limit of the car, "they drive the CAR, not the TRACK."
08-25-2017, 12:17 PM
#109
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In the former comparisons, the performance of the more balanced ratio cars can be easily duplicated in cars with an excess of power to grip simply by introducing a "throttle artist" behind the wheel!
On the latter, my opinion is that the limitations of the raceoptimal sim inject serious flaws in the way it calculates the result. I have little actual race and track day data, by leading and proven drivers in a variety of cars, that is close to that generated by raceoptimal. Neat exercise, but of little value, IMO.
Here's an interesting page: http://geneura.ugr.es/cig2012/papers/paper76.pdf
There is Bosch LapSim, but IMO, the easiest, most approachable lap sim software for club level drivers (but suitable for pro teams) is Claude Rouelle's OptimumG sim, OptimumLap.
Take a look here: http://www.optimumg.com/race-prep-an...tion-exercise/
Here is an awesome little article: http://blog.caranddriver.com/the-phy...est-lap-times/
I do have to say, drivers are MOST effective when, as Ross Bentley says, when probing the limit of the car, "they drive the CAR, not the TRACK."
On the latter, my opinion is that the limitations of the raceoptimal sim inject serious flaws in the way it calculates the result. I have little actual race and track day data, by leading and proven drivers in a variety of cars, that is close to that generated by raceoptimal. Neat exercise, but of little value, IMO.
Here's an interesting page: http://geneura.ugr.es/cig2012/papers/paper76.pdf
There is Bosch LapSim, but IMO, the easiest, most approachable lap sim software for club level drivers (but suitable for pro teams) is Claude Rouelle's OptimumG sim, OptimumLap.
Take a look here: http://www.optimumg.com/race-prep-an...tion-exercise/
Here is an awesome little article: http://blog.caranddriver.com/the-phy...est-lap-times/
I do have to say, drivers are MOST effective when, as Ross Bentley says, when probing the limit of the car, "they drive the CAR, not the TRACK."
I remember looking at that paper a while back. It seems to be focused on optimization algorithms, rather than comparisons of vehicles. But it does make this statement:
"... finding the optimal racing line requires to search for the optimal trade-off between racing the shortest distance and racing fast. Of course, such an optimal trade-off also depends on the racing car dynamics, i.e., it is different for different car models, and on the sequence of the track segments (e.g., the ideal line through the same turn might change if it is followed by a straight or a tight turn)."
That ties into the concept that time elapsed is a function of both distance traveled and speeds along the path traveled. This video covers all of this well (yes, I'm a big fan of Adam's work!):In that blog article, I think the author may be placing too much emphasis on maximizing speed at corner exit rather than minimizing lap time. It's a reasonable rule of thumb, but when getting down to last second or fractions of a second, the examples in Adam's video illustrate that the rule of thumb doesn't always work.
Agreed with your point about focusing on driving the car rather than the track. That's consistent with my comment about most drivers (including me) losing time mainly due to how far they're below the limits rather driving a suboptimal line.
Thanks for reference to OptimumG, I'll take a look (I started to take the test, but will need a calculator for that one!).
I've been really bogged down with work for months, and it's fun to get back to talking about driving.
08-25-2017, 12:47 PM
#110
Burning Brakes
I've driven a lot of different types of cars over the last few years and I honestly can't think of a single time where I used a different "line" because of what chassis I was driving at the time. With the exception of avoiding some curbs in prototypes where you jump them in GT's... but it didn't really change my "line".
The things that change are:
* initial brake zone (some cars get much deeper than others).
* attitude of the car at entry/mid corner (rotation, some need more than others).
* initial throttle point and application curve (ie: the McLaren GT3 you have to get to power way early because of turbo lag.)
** hint, the last 2 are heavily dictated by the differential setup in the car....
The things that don't change are:
* turn in point.
* apex.
* track out.
While I may not be super fast, I've driven with plenty of co-drivers who are and who's results are directly effected by how fast I am. If they could tell me or show me a faster way, they would have by now.
IMO, what holds a lot of people back is overanalyzing things that don't matter. Again, which is why a good coach is super critical if you want to improve quickly and go fast. If you just want to have fun goofing around with your friends or bench racing on the internet, that's a different hobby...
-mike
The things that change are:
* initial brake zone (some cars get much deeper than others).
* attitude of the car at entry/mid corner (rotation, some need more than others).
* initial throttle point and application curve (ie: the McLaren GT3 you have to get to power way early because of turbo lag.)
** hint, the last 2 are heavily dictated by the differential setup in the car....
The things that don't change are:
* turn in point.
* apex.
* track out.
While I may not be super fast, I've driven with plenty of co-drivers who are and who's results are directly effected by how fast I am. If they could tell me or show me a faster way, they would have by now.
IMO, what holds a lot of people back is overanalyzing things that don't matter. Again, which is why a good coach is super critical if you want to improve quickly and go fast. If you just want to have fun goofing around with your friends or bench racing on the internet, that's a different hobby...
-mike
08-25-2017, 01:08 PM
#111
Rennlist Member
Yep
Paralysis by over analysis
Paralysis by over analysis
08-25-2017, 01:10 PM
#112
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I've driven a lot of different types of cars over the last few years and I honestly can't think of a single time where I used a different "line" because of what chassis I was driving at the time. With the exception of avoiding some curbs in prototypes where you jump them in GT's... but it didn't really change my "line".
I don't actually pay much attention to line when I'm driving - my attention is mostly on how well I'm generating and using grip, and the line winds up being an outcome of that (I think that's essentially what Peter was alluding to). My line varies as conditions change, I make mistakes, etc.
08-25-2017, 01:51 PM
#113
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I've driven a lot of different types of cars over the last few years and I honestly can't think of a single time where I used a different "line" because of what chassis I was driving at the time. With the exception of avoiding some curbs in prototypes where you jump them in GT's... but it didn't really change my "line".
The things that don't change are:
* turn in point.
* apex.
* track out.
IMO, what holds a lot of people back is overanalyzing things that don't matter.
-mike
The things that don't change are:
* turn in point.
* apex.
* track out.
IMO, what holds a lot of people back is overanalyzing things that don't matter.
-mike
And you've driven quite a wide variety of cars...
08-25-2017, 04:47 PM
#114
Rennlist Member
ProCoach, I expect your intuition will be backed by lots of experience, so since you say it doesn't make any practical difference, while there might be a subtle theoretical difference, I'll be quite happy to trust that you're right. Ditto that of the other experienced racers echoing your comments. I do assume the context you're speaking to is racing within classes that could safely share a track.
To take a completely unreasonable example to show there is a theoretical difference in some cases, a kart with a 50mph top speed could be compared to a GT3 car. **Yes, this is absurd, but it's only a theoretical point and not a practical one - I've conceded the practical point already. The kart can essentially carry full 50mph speed through any corner on any full size track and never let off the throttle. So for the kart, the fastest line is the shortest possible path - connecting straight lines between every corner and ignoring basically everything else about the track. The GT3 car will take what we'd consider to be a normal line. That's not going to be the shortest possible path every time as corner speed needs to be maximized to get the best lap time. So in theory it's different.
That said, in practice, it sounds like you and others are all saying that everyone in any reasonable race setting will be running the same line, and other variables like driving style and setup might make more difference than these theoretical ideal line concepts. While that doesn't invalidate the theory, it makes it reasonable to neglect and ignore.
To take a completely unreasonable example to show there is a theoretical difference in some cases, a kart with a 50mph top speed could be compared to a GT3 car. **Yes, this is absurd, but it's only a theoretical point and not a practical one - I've conceded the practical point already. The kart can essentially carry full 50mph speed through any corner on any full size track and never let off the throttle. So for the kart, the fastest line is the shortest possible path - connecting straight lines between every corner and ignoring basically everything else about the track. The GT3 car will take what we'd consider to be a normal line. That's not going to be the shortest possible path every time as corner speed needs to be maximized to get the best lap time. So in theory it's different.
That said, in practice, it sounds like you and others are all saying that everyone in any reasonable race setting will be running the same line, and other variables like driving style and setup might make more difference than these theoretical ideal line concepts. While that doesn't invalidate the theory, it makes it reasonable to neglect and ignore.
08-25-2017, 05:01 PM
#115
Rennlist Member
...
IMO, what holds a lot of people back is overanalyzing things that don't matter. Again, which is why a good coach is super critical if you want to improve quickly and go fast. If you just want to have fun goofing around with your friends or bench racing on the internet, that's a different hobby...
-mike
IMO, what holds a lot of people back is overanalyzing things that don't matter. Again, which is why a good coach is super critical if you want to improve quickly and go fast. If you just want to have fun goofing around with your friends or bench racing on the internet, that's a different hobby...
-mike
In this case I think the lesson is that any theoretical difference in "ideal lines" is small enough to be insignificant in practical settings.
Thanks to all for interesting discussion.
08-25-2017, 05:37 PM
#117
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To take a completely unreasonable example to show there is a theoretical difference in some cases, a kart with a 50mph top speed could be compared to a GT3 car. **Yes, this is absurd, but it's only a theoretical point and not a practical one - I've conceded the practical point already. The kart can essentially carry full 50mph speed through any corner on any full size track and never let off the throttle. So for the kart, the fastest line is the shortest possible path - connecting straight lines between every corner and ignoring basically everything else about the track. The GT3 car will take what we'd consider to be a normal line. That's not going to be the shortest possible path every time as corner speed needs to be maximized to get the best lap time. So in theory it's different.
Randy Pobst touches on these points when comparing racing high-power vs low-power cars:
http://www.randypobst.com/index.cfm?...e&mag_id=14878
08-25-2017, 06:36 PM
#118
Drifting
With all due respect, a car's limit is static. What you are describing (I.e., "unsticking the car") is what is actually known as reaching a tire's limit of traction/adhesion. Contrary to popular belief, when a tire reaches its traction limit, it doesn't simply break away resulting in the the car spinning out of control. A tire's traction limit is actually achieved within a range of slip angle. Beyond that range, the tire starts to lose grip progressively as the coefficient of friction drops. Some tires 'breakaway' progressively while others are more snappy, (I.e., for a car equipped with a given tire, its limit is STATIC, as the optimal slip angle is a known factor). What you are describing is a driver driving AT the tire's limit of adhesion/traction which is over a range of slip angle.
Driving a car AT IT'S LIMIT, requires the driver to attain and manage to the tire's slip angle to achieve the car's optimal cornering limit. A known fact is that many inexperienced driver's do not account for changes in track conditions (I.e., cool morning, vs hot afternoon) or tire condition (e.g., changes in tire pressure throughout the track day AND changes in tire wear over the course of a 2-3 day DE weekend). These factors AFFECT the tire's coefficient of friction and the size of the tire's contact patch which alters the tire's behavior, making it challenging for driver's to gauge a tire's limit consistently.
Remember the optimal slip angle HAS NOT CHANGED, the tire's characteristics HAS. The best drivers can make the adjustments, most of us (myself included) struggle with this. This starts to get very technical but as a driver I strive to understand these technical points which affect my car's behavior on the track as it dictates the adjustments that I make throughout my DE weekend.
A car's limit is FIXED for any given section of a track, based on what I described earlier, what changes are the track and tire conditions which necessitates changing driver inputs to consistently achieve that limit. Hope this helps.
Driving a car AT IT'S LIMIT, requires the driver to attain and manage to the tire's slip angle to achieve the car's optimal cornering limit. A known fact is that many inexperienced driver's do not account for changes in track conditions (I.e., cool morning, vs hot afternoon) or tire condition (e.g., changes in tire pressure throughout the track day AND changes in tire wear over the course of a 2-3 day DE weekend). These factors AFFECT the tire's coefficient of friction and the size of the tire's contact patch which alters the tire's behavior, making it challenging for driver's to gauge a tire's limit consistently.
Remember the optimal slip angle HAS NOT CHANGED, the tire's characteristics HAS. The best drivers can make the adjustments, most of us (myself included) struggle with this. This starts to get very technical but as a driver I strive to understand these technical points which affect my car's behavior on the track as it dictates the adjustments that I make throughout my DE weekend.
A car's limit is FIXED for any given section of a track, based on what I described earlier, what changes are the track and tire conditions which necessitates changing driver inputs to consistently achieve that limit. Hope this helps.
08-25-2017, 06:40 PM
#119
Rennlist Member
Yes
08-25-2017, 07:03 PM
#120
I'm in....
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I've driven a lot of different types of cars over the last few years and I honestly can't think of a single time where I used a different "line" because of what chassis I was driving at the time. With the exception of avoiding some curbs in prototypes where you jump them in GT's... but it didn't really change my "line".
The things that change are:
* initial brake zone (some cars get much deeper than others).
* attitude of the car at entry/mid corner (rotation, some need more than others).
* initial throttle point and application curve (ie: the McLaren GT3 you have to get to power way early because of turbo lag.)
** hint, the last 2 are heavily dictated by the differential setup in the car....
The things that don't change are:
* turn in point.
* apex.
* track out.
While I may not be super fast, I've driven with plenty of co-drivers who are and who's results are directly effected by how fast I am. If they could tell me or show me a faster way, they would have by now.
IMO, what holds a lot of people back is overanalyzing things that don't matter. Again, which is why a good coach is super critical if you want to improve quickly and go fast. If you just want to have fun goofing around with your friends or bench racing on the internet, that's a different hobby...
-mike
The things that change are:
* initial brake zone (some cars get much deeper than others).
* attitude of the car at entry/mid corner (rotation, some need more than others).
* initial throttle point and application curve (ie: the McLaren GT3 you have to get to power way early because of turbo lag.)
** hint, the last 2 are heavily dictated by the differential setup in the car....
The things that don't change are:
* turn in point.
* apex.
* track out.
While I may not be super fast, I've driven with plenty of co-drivers who are and who's results are directly effected by how fast I am. If they could tell me or show me a faster way, they would have by now.
IMO, what holds a lot of people back is overanalyzing things that don't matter. Again, which is why a good coach is super critical if you want to improve quickly and go fast. If you just want to have fun goofing around with your friends or bench racing on the internet, that's a different hobby...
-mike